Print yourself a treat: how to modify a 3Drag printer to print chocolate

Oct. 22, 2014 | By Alec

3D Printing actually edible, affordable and long-last lasting food: this has been one of the greatest challenges and goals of the 3D printing industry. Sure, more and more printers capable of printing highly-detailed and wonderful objects are being released every year, but deep down every developer is still dreaming about the food replicator from Stark Trek.

Fortunately, some wonderful advances have already been made into producing an actual food printer. In recent months we've seen wonderful projects like the F3D Pizza Printer and the Edible Growth printing project, while the Foodini is will be released in mere months from now. Perhaps a marketable and affordable printer is just a few years away.

And this week Open Electronics shared a cool tutorial that will allow you to modify a 3Drag 3D printer, a quite typical RepRap FDM printer, with a pastry bag. Why a pastry bag? Well, this will enable it to print chocolate as well! And not just a single type of chocolate, but just milk, white and dark chocolate in just about any shape you can think of.

This adds a new level of convenience to 3D food printing. Why purchase a specialized printer if you can just add a very specific extrusion head to your own desktop 3D printer and print yourself a treat? Furthermore, it works with just about any STL file you'd commonly use to print plastic, making it a very easy and accessible technology. So why print that rabbit in PLA if you could do it in chocolate?

Central in this is their 3Drag FDM 3D printer, that is capable of working with just about any type of filament as long as its melting point is relatively low. This even opens the floor for speculation about just about any moldable food, like 'cream, chocolate, jellies, and soft batters, allowing you to produce sweet and savory products for decorations or other shapes'. However, this tutorial is specifically focusing on chocolate, but who knows what it will be capable of?

While their tutorial focuses specially on this printer brand, the whole process is relatively straight-forward, so a handy tinkerer should be capable of adjusting it to suit their particular desktop printer as well. All this definitely makes it worth checking out, even for those of you who don't have a 3Drag. However, as this project is quite a challenge, it might be more suited for those engineering types amongst you.

Check out the 3Drag chocolate 3D printer in action here:

Printing with chocolate

Obviously, there are a few steps that are key to printing chocolate. The first of these is the melting phase, which is essential for any type of printer.

Fortunately, the 3Drag is already capable of bringing chocolate to the melting point. Adding a special type of extruder to replace the one used for plastic, also enables the machine to keep the chocolate at about 32-33 degrees Celsius, which is a printable temperature. Basically, this is achieved through a common 60 ml syringe, attached to which is a NEMA17 stepper motor which drives its heater.

This is also the tempering temperature, which is very important to maintain. Any higher or lower will make the chocolate unsuitable for printing larger objects. 'For this reason, the control board constantly detects the temperature of the heater thanks to a NTC 100 kohm thermistor installed directly on the body of the aluminium cylindrical heater.' The loss of "tempering" of the chocolate would make impossible to print objects that develop in height, and then the chocolate itself would not be able to solidify at room temperature (24 ÷ 27 ° C).'

As will be seen in the modification tutorial, the syringe is inserted into an aluminum cylinder which not only supports the construction, but also transfers heat. This will help keep the chocolate in the syringe 'pre-softened', significantly improving the printing results.

Aside from the temperature, you also have to think about the chocolate cooling time, which affects the printing speed. 'In fact, depositing a layer of melted chocolate on a lower layer not yet solidified can deform the object; so the application of a layer must be carried out only when the underlying one is cool enough to bear both the weight of the chocolate above and the heat supplied by the melted chocolate deposed.'

This isn't an insurmountable problem, as the tests with the 3Drag revealed that you can still print with a bit of speed. However, it does mean it's very important to keep an eye on the printing process and adjust accordingly. You could, like the 3Drag team did, speed up the cooling process an airflow cooling system. 'we decided to use Peltier cells, […] this solution has proven to be the best.'

However, the team of Italian engineers also advises you to follow a printing speed of a maximum 20 mm per second, giving the individual layers enough time to cool down properly.

Modifying your 3D Printer

All this obviously means you need to make a few adjustments to your printer. However, this consists almost entirely of modifying an extruder. 'Therefore, you have to remove the original head from the horizontal rail of the print head holder and fit the new head, which consists of a syringe and its special housing that has the dual responsibility to support and heat, as well as the endless screw mechanism that presses on the piston to control the injection of the melted chocolate.'

The necessary extruder can be purchased on their website here. It will cost you some €145. This will include: a 60 ml syringe for medical use with central attack "Luer Lock" with a needle of 1.2 mm; a cylindrical aluminium body; cover needle; an aluminium guide; an aluminium plate 4 mm; an angle bracket for mounting in aluminium extruder in the arm of the printer 3Drag; a threaded rod; 2 ball bearings; supports for fixing made of Delrin; a heating element and a NTC thermistor axial 100 Kohm.

This will still, however, require you to install a separate motor. You could buy one on their website, or use one still lying around.

To assemble and mount your very own chocolate extruder, simply follow the comprehensive 15 steps you can find in their tutorial here.

All that then remains is updating your corresponding firmware. The 3Drag uses Marlin V1 firmware, which comes with a whole series of protections that prevent your machine from printing at any temperature below 170 degrees Celsius. While wonderful when working with plastic, these need to be overridden when printing chocolate at 33 degrees Celsius.

But once you've done all this, congratulations! You can now start printing your own chocolate treats, decorations and cool edible objects. While it will cost you a bit of money to complete this project –and it still remains to be seen how effective it is on other printers – this 3Drag modification is nonetheless a wonderful initiative that is bringing food printing to the public.